The present invention relates to a device for relative angular adjustment between two drive-connected elements rotating at the same rotational speed.
Devices of the type mentioned above are described, for example, in German Published Patent Application No. 196 54 926 and are provided for the relative angular adjustment of the camshaft in relation to the crankshaft driving the latter, at the transition between the camshaft-side chain wheel, rotating at the same rotational speed as the camshaft, and the camshaft, as elements adjustable in relation to one another in terms of their relative angular position. Angular adjustment occurs by an axially displaceable transmission member which carries a helical toothing radially on the inside and radially on the outside, the radially inner and the radially outer helical toothings being set in opposite, so that, during axial displacement of the transmission member, the elements connected via the transmission member are adjusted in relation to one another in terms of their relative angular position. The displacement of the transmission member occurs via a hydraulically loadable actuating piston, in the supply path of which is located a control slide acted upon via a solenoid valve.
Devices of this type have proved appropriate in practice and make it possible to apply the necessary actuating forces by connection to the oil circuit of the internal combustion engine. On the other hand, however, their mechanical construction is relatively complicated, and they also require electrical activation for the actuating magnets in addition to connection to the oil circuit of the internal combustion engine.
It is an object of the present invention to provide a device for relative angular adjustment between two drive-connected elements rotating at the same rotational speed, which has a simplified construction and a reduced space requirement.
The above and other beneficial objects of the present invention are achieved by providing a device as described herein. In this case, use is made of an electronically commutated electric motor as an actuating drive, of which the stator forming the coil part is fixed in position for support, so that simple line feeds are provided, and of which the rotor, as a part fitted with permanent magnets, is assigned to one of the rotating elements and may be carried via the latter. This configuration avoids interfaces between moved and non-moved parts with regard to control and electrical power supply, and, as regards the rotor, it makes it possible to have a simple construction which is insensitive to rotational speed and, in conjunction with a corresponding gear connection to the transmission member, also makes it possible to implement high transmission ratios, so that comparatively low drive powers are required.
When the device according to the present invention is used on a camshaft adjuster for internal combustion engines, in which the transmission member is located between the chain wheel driven by the crankshaft and concentric to the camshaft and the camshaft, it may be beneficial to support the rotor against the camshaft, this support including, for example, a gear connection to the transmission member, so that a simple construction is obtained, the rotor, as a ring gear, being supported on planet wheels which are concentric to the camshaft and which are mounted in a carrying housing supported on the camshaft and are continued in coaxial spindles which engage into the transmission member and via which the transmission member may be adjusted axially.
The transmission member may be configured as a sliding block which includes a helical toothing in each case radially on the outside and radially on the inside, the two helical toothings being set in opposition and meshing with corresponding helical toothings of the chain wheel and of the camshaft, so that an axial adjustment of the transmission member configured as a sliding block is accompanied by a rotation of the chain wheel and of the camshaft in mutually opposite directions of rotation, this rotation resulting in the intended angular adjustment.
In a solution of this type, an axial adjustment of the sliding block is possible, e.g., by a rotary drive via the spindle, but not by axial forces introduced via the helical toothings, so as to afford a self-locking connection, by which the chain wheel and the camshaft are connected fixedly in terms of rotation relative to one another in a concentric position, as long as a desired angular adjustment is not performed via the drive of the spindle. Accordingly, the carrying housing for the support of the spindles or of the planet wheels in relation to the camshaft is fixed in a circumferential direction, relative to the camshaft, via the spindles engaging into the sliding blocks, as long as the rotor is not driven at a rotational frequency deviating from that of the camshaft.
A spindle drive of this type for the transmission members makes it possible to have very high transmission ratios due to the choice of the spindle thread and because of the relatively large diameter of the rotor which meshes via the ring gear with the gearwheels mounted in the carrying housing and arranged in a planet-like manner in relation to the camshaft.
If a relative angular adjustment between the two elements, i.e., the chain wheel and the camshaft, is to be performed via the actuating drive, the rotating field of the stator is excited at a frequency different from the rotational frequency of the camshaft. The difference between the rotational frequency of the camshaft and the exciting frequency of the stator corresponds to the resulting rotational frequency of the rotor. At an exciting frequency of the stator corresponding to the rotational frequency of the camshaft, therefore, the rotor rotates synchronously with the camshaft, so that, on the assumption that the stator is at the corresponding exciting frequency, the transmission member is also held via the spindles in an axial position assigned to a given relative angular position between the chain wheel and the camshaft.
Instead of a gear system of the abovementioned type, it is also possible to provide between the chain wheel and the camshaft a worm drive which adjusts the chain wheel and the camshaft in terms of their angular position when the actuating drive is activated correspondingly.